From German patent application 26 22 794 such a device and method are known. This document shows a milking device for pneumatically milking a cow and subsequent cleansing or disinfecting the teats of the cow's udder, with a system of four milk extractors, each comprising a teat cup which at one end is provided with an open lining and with the other end is connected to a milk line to a common milk collection chamber for the milk from the cow in question, each cup having a connection to a source of changing vacuum, and an outflow opening of a line for the supply of cleansing liquid being arranged in the wall of a teat cup.
When using this known device the method used is to first place the teat cups around the cow's teats, after which the cow is milked by means of the changing vacuum. After finishing milking the cow, while the cow's teats are still in the teat cups, a certain quantity of cleansing liquid is squirted into the teat cup by means of a pump. Said liquid will disinfect the teat and the space in the teat cup, but will subsequently together with the milk residue in the teat cup deposit on the inner wall of the teat cup. The liquid will then have the chance, even before the teat cups have been removed from the teats, to go back past the inner wall or from the teat back down and thus partially end up in the milk line. As a result milk residues of a cow will not only be left in the teat cup and milk line but will thus also transfer a contamination from the one cow to the other. Moreover, when milking the next cow residues of the cleansing liquid that have ended up in the milk line will subsequently end up in the central milk storage to which it is connected and therefore in the milk to be delivered.
A number of suggestions for improvements of this have been described in applicant's earlier International patent application WO 99/66787. In both of these suggestions use is made of a leaf spring, which in the unloaded situation abuts the inner surface of the milk extractor and then closes off a supply chamber for cleansing medium, and which in a loaded situation closes off the passage in the milk extractor to the downstream portion thereof and clears the way for supplied pressurized (by compressed air) cleansing medium. In that way when discharging a cleansing medium, and the aforementioned problem therefore exists, it is counteracted that during discharging the cleansing medium said medium may end up in the milk line and thus in the milk collection chamber. In a first embodiment, the spring leaf is operated by means of a pusher, which is connected to a separate pressure line.
In a second embodiment, which is simpler as to construction, the leaf spring is directly operated by the pressure of the cleansing medium itself.